In recent months we’ve been looking at science writer Matt Williams’s coverage of the many reasons (links below) people have advanced as to why we do not see extraterrestrials except at the movies. Last Saturday, we considered the Aurora Hypothesis: Given the difficulties and risks of space travel, extraterrestrials with advanced technology may have visited Earth only one in a million years, researchers say.

Another hypothesis that Williams has examined is the Dark Forest Hypothesis. He begins by noting that space exploration necessarily conjures up the notion of risk: “Words like Rim, Edge, Fringe, and Verge, Beyond, Perimeter, and Periphery all conjure up feelings of intrigue and anxiety – no doubt, in different measures for different people”:

This particular proposed resolution to Fermi’s Paradox question is a very recent addition. It takes its name from the novel The Dark Forest by famed Chinese science fiction writer Liu Cixin. This book is the second installment in the Remembrance of Earth’s Past series, which deals with the prospect of an impending alien invasion. In a fascinating twist, this invasion was actually invited by a group of disillusioned humans!

Matt Williams, “Beyond “Fermi’s Paradox” XVI: What is the “Dark Forest” Hypothesis?” at Universe Today

Liu Cixin’s The Dark Forest (2008) is the second book in the Three-Body Trilogy, Remembrance of Earth’s Past. The first book is The Three-Body Problem (2006) and the third is Death’s End (2008). Liu (pictured in 2015) is a winner of the Hugo Award for science fiction and of many other awards.

So now, what’s the thesis? According to reviewer Rachel Cordasco at Tor,

In the world of this series, the fallout of contact becomes the story of humanity. Given humanity’s relatively short time (so far) on this planet, the four hundred years that Liu’s characters have to prepare for the coming of the Trisolarans is quite generous. Even then, squabbling and power-grabs (along with Trisolaran technology) interfere with the need to come up with a clear plan for Earth’s first encounter with Trisolarans. This is precisely Liu’s point: that it’s reckless to try and contact alien species when a) we don’t even have our own house in order and b) we have to assume that other intelligent life in the universe is actually hostile. And why not? If you’re wandering around in a dark forest, do you really want to take the chance and expose yourself to those who might want your stuff or just one less potential threat?

Liu goes further than simply forcing us to think beyond our own planet and consider our wider galactic neighborhood; with Death’s End, he expands our perspective even further, introducing universes of two and even four dimensions. He asks us to think about (and shudder at) the existence of a disembodied brain being studied by Trisolarans for what might seem like an eternity. And then, as if our minds weren’t already reeling, he pushes the boundaries even further, asking us to think about our universe’s relation to other universes.

Just for the record, a 19th century British schoolteacher, Edwin Abbott, wrote a short novel, Flatland (1884, now free online at the link), about a two-dimensional universe — with a trip into a one-dimensional universe. The idea isn’t new though the treatment may be.

One of Liu’s characters introduces a sociology of the universe — studying alien civilizations for patterns. In Williams’s telling,

Ye introduces two key axioms, which state that: 1) survival is the primary need of civilizations, and 2) civilizations continuously grow and expand, but the total matter in the universe remains constant. In other words, the finite nature of resources will ultimately pit one civilization against another as they all struggle to sustain their growth.

This alone will not make conflict inevitable, but Ye introduces two other assumptions to the mix: “Chains of Suspicion” and “Technological Explosion.” Basically, civilizations could essentially be either malevolent or benevolent, depending on a number of factors. For their part, malevolent civilizations are likely to attack others due to their nature and/or the desire for territory, resources, etc.

Matt Williams, “Beyond “Fermi’s Paradox” XVI: What is the “Dark Forest” Hypothesis?” at Universe Today

Benevolent civilizations are less likely to do that, we are told, but they may resort to a “Shoot first and ask questions later” strategy. In any event, as Williams notes, they may be less likely to want to go spacefaring or even try to contact extraterrestrial civilizations.

In Liu’s words (in translation), as quoted by Williams, “The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him.”

Fraser Cain develops the idea here:

Here’s an excerpt from The Dark Forest.

Now, what to make of the thesis that we can use sociology to determine what extraterrestrial intelligences (ETs) might be like? Two questions arise:

● We assume that the ETs will have the same assumptions and goals that we do. But we really don’t know that. Sociology, as we know it, concerns human beings on this planet. The underlying unity of the human race enables sociologists to posit universal theories. But elsewhere, with different sorts of intelligent beings, things might be quite different.

Fantasy novelist H. P. Lovecraft (1890–1937) created a number of works involving beings with totally different lives and aspirations from our human ones: “Lovecraft’s major inspiration and invention was cosmic horror, the basic premise of which is that the true workings of the universe are beyond human comprehension and that humanity’s place in the cosmos is terrifyingly insignificant.” – Lovecraft Fandom. It might not be quite that bad but it could be somewhere in between.

● Sad to say, sociology today isn’t performing well even with humans on Earth. Some readers may be aware of the Sokal hoaxes that have been perpetrated on sociology journals in recent decades: Intentionally meaningless papers are accepted and published as the famous Grievance Studies Affair revealed in 2018:

The paper that was published in Gender, Place and Culture seems downright silly. “Human Reaction to Rape Culture and Queer Performativity at Urban Dog Parks in Portland, Oregon” claims to be based on in situ observation of canine rape culture in a Portland dog park. “Do dogs suffer oppression based upon (perceived) gender?” the paper asks.

Yascha Mounk, “What an Audacious Hoax Reveals About Academia” at The Atlantic

Mounk adds, “If certain fields of study cannot reliably differentiate between real scholarship and noxious bloviating, they become deeply suspect.”

Fortunately, The Dark Forest and the hypothesis named after it can stand on their own, as a plea for realism about what we may expect to encounter if we, in Star Trek’s terms, boldly go.

Note: The photo of Liu Cixin is courtesy Opacity from Chicago – Geek Bar Tor authors event CC BY-SA 2.0.

You may also enjoy these accounts of why we do not see the aliens:

1.Are the Aliens We Never Find Obeying Star Trek’s Prime Directive? The Directive is, don’t interfere in the evolution of alien societies, even if you have good intentions. Hence the Zoo hypothesis. Assuming the aliens exist, perhaps it’s just as well, on the whole, if they do want to leave us alone. They could want to “fix” us instead…

2.How can we be sure we are not just an ET’s simulation? A number of books and films are based on the Planetarium hypothesis. Should we believe it? We make a faith-based decision that logic and evidence together are reasonable guides to what is true. Logical possibility alone does not make an idea true.

3.Did the smart machines destroy the aliens who invented them? That’s the Berserker hypothesis. A smart deadly weapon could well decide to do without its inventor and, lacking moral guidance, destroy everything in sight. Extinction of a highly advanced civilization by its own lethal technology may be more likely than extinction by natural disaster. They could control nature.

4.Researchers: The aliens exist but they are sleeping… And we wake them at our peril. The Aestivation hypothesis is that immensely powerful aliens are waiting in a digitized form for the universe to cool down from the heat their computers emit.

5.Maybe there are just very few aliens out there… The Rare Earth hypothesis offers science-based reasons that life in the universe is rare. Even if life is rare in the universe, Earth may be uniquely suited to space exploration, as the Privileged Planet hypothesis suggests.

6.Does science fiction hint that we are actually doomed? That’s the implication of an influential theory, the Great Filter hypothesis, as to why we never see extraterrestrials. Depending how we read the Kardashev scale, civilizations disappear somewhere between where we are now and the advanced state needed for intergalactic travel.

7.Space aliens could in fact be watching us. Using the methods we use to spot exoplanets. But if they are technologically advanced, wouldn’t they be here by now? The Hart-Tipler conjecture (they don’t exist) is, of course, very unpopular in sci-fi. But let’s confront it, if only to move on to more promising speculations.

8.Is the brief window for finding ET closing? According to some scenarios (the Brief Window hypothesis), we could be past our best-before date for contacting aliens. Of course, here we are assuming a law of nature as to how long civilizations last. Can someone state that law? How is it derived?

9.What if we don’t see aliens because they have not evolved yet? On this view, not only did we emerge during a favorable time in the universe’s history but we could end up suppressing them. The Firstborn hypothesis (we achieved intelligence before extraterrestrials) lines up with the view that humans are unique but sees that status as temporary.

10. The aliens exist—but evolved into virtual reality at a nanoscale. That’s the Transcension Hypothesis, the latest in our series on science fiction hypotheses as to why we don’t see extraterrestrials.
    On this view, after a Singularity the ETs become virtual intelligences, exploring inner space at an undetectably small scale.
11. Is intelligent life in the universe living in interior oceans of planets and moons? The Ocean Planets Hypothesis is that intelligent beings may flourish in the interior oceans of the moons of gas giant planets — or within exoplanets — but they are trapped there.
    If intelligent life forms are trapped in the interior oceans of rocky moons and planets, Earth is a special planet—much better suited to space exploration.
12. Is real-world space travel just too daunting for ET? That’s the Percolation Hypothesis as to why we don’t make contact with aliens. They can’t overcome the laws of physics, any more than we can. If there is a purpose behind the universe, maybe the aliens and we weren’t intended to meet. That’s worth considering, given the physics barriers.

13: The Aurora Hypothesis: ET could risk only rare contact with us. Given the difficulties and risks of space travel, extraterrestrials with advanced technology may have visited Earth only one in a million years, researchers say. After centuries of modern science, we are just now looking for fossil bacteria on Mars, not without risk. ET may be in the same position.